EXCHANGE 


vr/VR 


A  Spectrographic  Study  by  Means  of  a 
Grating  (Replica)  Spectroscope  and  The 
Determination  of  The  Wave  Lengths 
of  The  Arc  Spectrum  of  Tantalum 


JO 

XLJSH3AINQ 


2H1 


PRESENTED  TO  THE 

FACULTY  OF  VANDERBILT  UNIVERSITY 

AS  A  THESIS,  FOR  THE  DEGREE  OF  DOCTOR  OF  SCIENCE, 

BY  ALLAN  F.  ODELL,  M.  S. 


A   Spectrographic  Study  by  Means 
of  a  Grating  (Replica)  Spectro- 
scope   and   The    Determina- 
tion of  The  Wave  Lengths 
of  The  Arc  Spectrum 
of  Tantalum. 


PRESENTED  TO  THE 

FACULTY  OF  VANDERBILT  UNIVERSITY 

AS  A  THESIS  FOR  THE  DEGREE  OF 
DOCTOR  OF  SCIENCE 


BY  ALLAN  F.  ODELL,  M.  S. 


CONTENTS. 


Page 

Acknowledgment 3 

Dedication 4 

Introduction 5 

Residues  Containing  Doubtful  Elements 6 

The  Arc 7 

The  Spectrograph 8-9 

Purification  of  Tantalum 9-10 

Methods  of  Measurement 10 

The  Comparator 10-11 

The  Comparator  Method 11-12 

The  Projection  Method 12 

The  Arc  Spectrum  of  Tantalum 14 

The  Spectrum  of  a  Clay  Residue 19 

Summary 20 


ACKNOWLEDGMENT. 

I  wish  to  express  my  sincere  appreciation  and  thanks  to  Dr. 
William  L.  Dudley,  of  this  University,  at  whose  suggestion  this 
research  was  commenced,  and  by  whom  it  has  been  directed. 


4698^2 


As  a  token  of  esteem  and  affection  to  my 
old  class-mate 

ERNEST  WILLIAM  GOODPASTURE 


INTRODUCTION. 


The  original  object  of  this  research  was  to  investigate  the 
contents  of  rare  elements  in  some  of  the  clays  of  the  South ;  and 
for  this  purpose,  samples  were  collected  from  as  many  different 
points  as  possible. 

The  manner  in  which  the  investigation  was  to  be  carried  out, 
was  to  separate  the  clay  into  its  various  constituents,  and  exam- 
ine these  in  the  spectroscope,  and,  if  unusual  elements  were  found, 
to  estimate  the  quantity.  To  give  an  example,  a  clay  was  treated 
thus :  It  was  first  qualitatively  analyzed  for  the  ordinary  elements, 
as  iron,  aluminum,  manganese,  calcium,  magnesium,  potassium, 
sodium,  etc.  The  precipitates  obtained  for  these  metals  were 
dried,  powdered,  and  put  in  the  arc  for  photographing  the  spec- 
trum. The  resulting  spectographs  were  examined,  and  the  lines 
carefully  measured.  In  this  manner,  the  spectra  of  the  rare  ele- 
ments would  identify  their  presence  without  making  the  tedious 
qualitative  examination  for  them  in  the  first  instance  necessary. 


RESIDUES  CONTAINING  DOUBTFUL  ELEMENTS. 

In  the  first  set  of  clays  examined,  three  specimens  from  Spruce 
Pine,  Alabama,  a  residue  was  obtained  which  gave  lines  of  Ti, 
and  another  element,  which  we  could  not  identify  from  its  spec- 
trum. The  method  by  which  this  residue  was  obtained  is  as 
follows:  The  clay  is  finely  pulverized  and  heated  with  a  mixture 
of  eight  parts  cone,  sulphuric  and  two  part  cone,  nitric  acid,  un- 
til solution  has  taken  place  and  only  a  white  siliceous  residue  is 
left.  By  this  method  the  majority  of  the  elements  are  taken 
into  the  solution.  It  is  diluted  with  water  and  the  siliceous 
matter  filtered  off.  The  Fe  and  Mn  and  some  rare  elements  are 
precipitated  from  the  filtrate  by  adding  an  excess  of  KOH.  The 
solution  is  again  filtered  and  the  precipitate  washed  on  the  filter. 
The  precipitate  is  then  dissolved  in  HC1,  and  the  resulting  solution 
treated  with  NrLjOH,  until  precipitation  occurs,  (NH4)  2Sx  is 
added  until  the  hydroxide  which  was  first  precipitated,  is  changed 
into  sulphide.  H2SO3  is  then  added  until  the  solution  clears, 
leaving  a  white  precipitate.  Ti,  Cb,  Ta,  etc.,  remain  in  the  precipi- 
tate, which  is  filtered  off  and  washed.  The  Fe,  Mn,  Cr,  etc.,  will  be 
in  the  filtrate.  The  precipitate  is  dried,  and  removed  from  the 
paper,  and  fused  with  Na2CO3  in  a  platinum  crucible.  The 
fusion  is  digested  in  cold  water  and  filtered.  The  precipitate 
is  treated  with  HC1,  and  to  the  resulting  solution  Na2S2O3 
added.  A  precipitate  is  gotten  which  is  designated  as  precipitate 
A.  This  precipitate  was  examined  under  the  spectroscope,  and 
will  be  referred  to  later.  If  the  filtrate  from  precipitate  A  is 
treated  with  KOH,  another  precipitate  is  gotten,  which  is  precipi- 
tate B,  and  which  has  not  yet  been  investigated,  as  the  quantity 
obtained  was  tpo  small.  The  filtrate  from  the  Na2CX>3  fusion 
is  made  acid  with  HC1,  and  the  CO2  expelled  by  boiling,  NH-4OH 
is  then  added,  and  the  excess  expelled  by  boiling.  Another  pre- 
cipitate is  obtained.  This,  also,  has  not  been  examined. 

Precipitate  A  gave  lines  for  Ti,  and  was  contaminated  by 
traces  of  Fe;  but  there  were  also  other  strong  lines  present, 
which  could  not  be  identified  in  the  spectra  of  either  of  these 
elements. 

As  tantalum  occurs  widely  distributed,  and  associated  with 
titanium,  some  lines  of  the  former  were  suspected  of  being  pres- 


ent  in  the  spectrum  of  precipitate  A.  And  as  no  arc  spectrum 
of  tantalum  has  been  made  heretofore,  and  as  the  continued  recur- 
rence of  this  element  would  present  serious  difficulty  in  the  future 
work  on  clays,  the  arc  spectrum  of  tantalum  has  been  made  be- 
tween ^3200  to  ^6300. 

The  apparatus  available  would  only  permit  of  the  measure- 
ment of  the  lines  to  the  fourth  place,  which  is  sufficiently  accurate 
for  all  practical  work. 


THE  ARC  USED. 

The  first  arc  used  was  a  closed  lantern  with  carbon  poles, 
but  as  so  many  bands  occurred  in  the  carbon  spectrum,  they 
obscured  the  fainter  lines,  and  the  carbon  poles  with  the  closed 
lantern  were  discarded  and  replaced  by  a  hand  feed  lantern  using 
copper  poles.  As  copper  gives  a  sharp  spectrum  with  lines  wide- 
ly distributed,  it  served  perfectly.  The  impurity  in  it  is  chiefly 
Fe,  and  this  assists  in  finding  standards  for  measurement.  The 
poles  are  5-16  of  an  inch  in  diameter,  and  are  turned  down  a 
half  inch  from  the  end  to  about  3-16  of  an  inch.  The  lower  pole 
is  cupped  out  for  receiving  the  substance.  The  cur- 
rent used  was  about  104  volts  and  four  to  six  am- 
peres. The  bottom  pole  containing  the  substance, 
was  used  as  the  positive  pole.  (Fig.  I.) 

An  attempt  was  made  to  secure  spark  spectra  of 
some  of  the  clay  residues,  but  as  these  were  usually  -i- 

in  the  form  of  a  fine  powder,  the  spark,  on  turning  on 
the  current,  would  brush  the  substance  off  the  pole 
immediately. 

In  taking  the  spectra  from  the  arc,  it  was  found 
that  by  shifting  the  upper  pole  slightly,  the  arc  could 
be  kept  constantly  on  the  fused  substance  on  the 
lower  pole,  thereby  diminishing  the  copper  cpectrum 
and  intensifying  the  spectrum  with  the  substance  to 
be  examined. 

Figure  1 


THE  SPECTROGRAPH. 

The  spectograph  used  is  one  of  special  construction,  and  de- 
signed by  Dr.  Dudley,  and  made  so  that  the  entire  spectrum  be- 
tween ^3000  and  ^6500  can  be  taken  on  one  plate. 

Its  construction  will  be  easily  understood  from  the  diagram. 
(Fig.  2.)  A  is  the  slit,  regulated  by  the  micrometer  screw  B 
which  adjusts  the  slit  in  fortieths  of  a  millimeter.  C  is  the  screw 
adjustment  which  focuses  the  light  from  A  on  to  the  lens  D, 
which  parallels  the  rays  upon  the  grating  G.  From  thence  they 
are  dispersed  upon  a  vertical  slit  at  H,  behind  which  is  arranged 
the  photographic  plate.  K  is  the  screw  which  raises  and  lowers 
the  table  L.  E  is  a  hinge,  regulated  by  F,  which  raises  and 
lowers  the  portion  of  the  spectrograph  at  M  so  that  the  extreme 
red  or  violet  may  be  taken  by  raising  or  lowering  it,  respectively. 
I  is  an  arrangement  for  moving  the  photographic  plate  before  the 
slit  H.  Upon  this  plate  about  twelve  spectra  can  be  taken.  This 
spectrograph  has  a  focus  of  2  1-2  feet,  and  uses  a  replica  grating 
with  20150  lines  to  the  inch.  The  size  of  the  plate  used  is  3^ 
by  4  inches.  The  instrument  is  capable  of  transmitting  wave 
lengths  to  about  2600. 

PURIFICATION  OF  TANTALUM. 

The  tantalum,  in  the  form  of  Ta2O5,  was  prepared  from  tan- 
talite  obtained  from  Pilbarra  Dist.  W.,  Australia.  The  method 
used  in  the  separation  and  purification  of  the  tantalum  is  a  mod- 
ification of  the  original  method  of  Wolcott  Gibbs  for  the  prep- 
aration of  Columbium  from  Columbite,*  and  is  as  follows:  The 
finely  powdered  tantalite  is  fused  with  twice  its  weight  of  KHF2 
in  a  platinum  dish,  until  the  tantalite  is  dissolved,  and  the  excess 
of  HF  is  driven  off.  The  fusion  is  dissolved  in  water,  and  the 
gangue  filtered  off.  The  filtrate  from  this  is  evaporated  a  little 
and  allowed  to  stand  to  crystallize.  If  crystals  do  not  form  on 
cooling,  it  is  evaporated  more  and  stood  aside  again.  In  this 
manner  successive  small  crops  of  tantalum  potassium  fluoride 
crystals  are  prepared.  These  are  kept  separate,  and  a  specimen 
of  Ta2O5  is  prepared  from  the  first  crop,  by  the  method  explained 
later,  and  is  examined  in  the  spectroscope.  This  first  crop  of 
crystals  of  the  double  fluoride  is  again  dissolved  in  water.  And 
fractionated  further,  a  specimen  of  Ta2O5  is  also  prepared  from 

*Am.  J.  Sc.  &  Arts  37,  357. 


10 

the  next  first  crop  and  examined  under  the  spectroscope  similarly. 
This  fractionation  and  recrystallization  of  the  double  fluoride  is 
continued  until  the  spectrum  of  the  specimen  of  Ta2Os  from  the 
last  crops  shows  no  loss  of  lines,  indicating  that  the  impurities 
have  vanished  through  repeated  recrystallization.  This  final 
crop  of  double  fluoride  crystals  is  dissolved  in  water  and  treated 
with  H2S  as  a  precaution  to  insure  the  absence  of  Sn,  W,  etc. 
The  precipitate,  if  any,  is  filtered  off,  and  the  filtrate  treated  with 
concentrate  H2SO4,  and  evaporated  to  dryness.  The  residue  is 
treated  with  water  and  Rochelle  salt.  All  metals  will  go  into 
solution  except  the  tantalum,  which  is  left  as  Ta2Os,  and  which, 
on  washing  well,  will  be  found  in  a  sufficiently  pure  condition 
for  spectroscopic  work. 

THE  METHODS  OF  MEASUREMENT. 

The  measurement  of  the  lines  is  made  in  two  different  man- 
ners. First  the  measurement  with  the  comparator,  by  which 
means  a  relative  number  is  given  to  each  line.  A  curve  is  then 
plotted  upon  cross  section  paper  from  which  this  number  can  be 
converted  into  wave  lengths.  The  error  of  this  method  is  about 
0.5  Angstrom  unit. 

The  second  manner  is  by  means  of  the  projection  method. 
The  plate  upon  which  is  the  spectrum  to  be  measured  is  put  in 
an  ordinary  projection  lantern  and  the  image  thrown  upon  a 
screen  from  twelve  to  sixteen  feet  removed.  The  lines  are  meas- 
ured by  means  of  a  centimeter  scale,  which  will  be  more  fully 
explained  later. 

THE  COMPARATOR. 

The  comparator  mentioned  above  was  made  to  order 
by  Zeiss  &  Co.  It  consists  of  two  moderately  high  power 
stationary  microscopes  mounted  six  inches  apart.  Beneath  these 
is  a  movable  stage,  half  of  which  has  a  scale  graduated  in  tenths 
of  millimeters  on  its  surface,  which  slides  back  and  forth  under, 
and  is  read  through  the  right-hand  microscope.  The  other  half 
of  the  stage  is  constructed  so  that  it  will  hold  a  plate.  It  has  in 
its  middle  a  slit  three-eighths  of  an  inch  wide,  which  traverses 
the  entire  length  of  the  surface  that  is  intended  to  hold  the  plate. 
When  the  stage  slides  back  and  forth,  this  slit  is  beneath  the 
left-hand  microscope,  and  is  free  to  receive  the  light  reflected  from 


11 

a  mirror  placed  beneath  the  stage,  directly  under  the  microscope. 

The  microscopes  are  about  twenty  diameters  in  power,  and 
have  the  usual  focusing  adjustment.  Each  has  beneath  the  eye- 
piece a  stationary  pointer,  and  two  parallel  wires  moving  hori- 
zontally and  governed  by  a  micrometer  screw  on  the  outside. 
The  pointer  of  the  left-hand  microscope  is  placed  directly  over 
the  lines  to  be  measured,  and  the  width  of  the  line  may  be  deter- 
mind  by  the  parallel  wires  and  micrometer  screw  attached  to  this 
microscope.  The  pointer  of  the  right-hand  microscope  has  the 
parallel  wires  placed  directly  across  it,  at  which  point  the  microm- 
eter screw  reads  zero.  The  parallel  wires  are  then  moved  across 
the  nearest  scale  number,  and,  then  reading  of  the  fractions  taken 
on  the  micrometer.  In  this  manner,  measurement  are  made  to 
the  one-thousandth  of  a  millimeter.  The  spectrum  to  be  meas- 
ured is  put  upon  the  slit  under  the  left-hand  microscope.  The 
stage  is  then  adjusted  so  that  some  arbitrary  number  is  under 
the  right-hand  microscope,  for  example,  40.000.  The  plate  is  then 
adjusted  under  the  microscope  so  that  some  known  line,  which 
is  used  as  a  standard,  comes  between  the  parallel  wires.  The 
stage  can  be  drawn  back  now  so  that  the  far  edge  of  the  spectrum 
is  under  the  microscope,  and  as  each  line  comes  between  the  cross 
wires,  the  scale  is  read  at  the  right-hand  microscope.  For  exam- 
ple, we  find  lines  in  the  copper  spectrum  on  numbers  39.025, 
41.000,  51.060,  etc.,  when  the  line  ^5179  is  set  on  40.000. 

THE  COMPARATOR  METHOD. 

Now  to  convert  these  numbers  into  wave  lengths,  a  chart 
must  be  drawn  upon  cross  section  paper.  Copper  has  in  its  spec- 
trum several  prominent  lines  which  are  easily  recognized.  There 
are  three  lines  in  the  red,  ^5218,  ^5153,  and  ^5105,  which 
read  on  the  comparator  39.025,  40.645,  and  41.800  respectively; 
two  lines  in  the  green,  ^4651  and  '-4275,  which  read  on  the 
comparator  52.900  and  62.340;  two  lines  in  the  violet,  ^4062 
and  ^4022,  on  the  comparator  67.720  and  68.710.  There  occur 
also,  several  iron  lines  with  the  copper  in  the  spectrum,  as  the 
copper  was  not  pure;  and  these  assist  in  plotting  the  curve. 

A  piece  of  cross  section  paper  is  taken  which  has  along  one  co- 
ordinate, the  wave  length  numbers,  and  along  the  other  the  com- 


12 

parator  scale  numbers.  (Fig.  3.)  As  the  measurement  of  the 
plate  commenced  in  the  red,  the  comparator  numbers  read  up, 
while  the  wave  lengths  read  down.  A  place  is  now  found  on 
the  chart  along  the  wave  length  co-ordinate  for ^5218,  and  along 
the  comparator  scale  co-ordinate  39.025.  If  the  two  points  found 
are  extended,  along  the  perpendicular  and  horizontal  lines  of  the 
cross  section  paper,  they  intersect  in  a  point,  which  is  the  starting 
point  of  the  curve.  The  other  lines,  of  which  we  know  the  wave 
lengths  and  the  comparator  reading,  are  placed  in  a  similar  man- 
ner. When  all  the  points  have  been  found,  they  are  connected 
by  a  line  which  forms  the  curve.  In  this  case,  where  the  diffrac- 
tion grating  was  used,  the  curve  is  so  slight  as  to  approximate  a 
straight  line.  Now  the  method  by  which  the  wave  lengths  are 
gotten,  is  to  take  the  comparator  reading,  find  its  place  along 
the  proper  co-ordinate,  extend  it  out  until  it  strikes  the  curve,  and 
drop  a  perpendicular  from  this  point  to  the  wave  length  co-ordi- 
nate, and  the  wave  length  is  read  off  this. 

THE  PROJECTION  METHOD. 

The  projection  method  has  the  double  advantage  of  being 
much  simpler  and  more  accurate,  and  the  relative  intensities  of  the 
lines  may  be  determined  with  greater  facility,  but  at  the  same 
time,  the  faint  lines  cannot  be  seen  and  measured  so  easily. 

For  this  purpose  it  is  only  necessary  to  place  the  plate  in  the 
lantern,  and  project  the  image  on  a  screen  twelve  to  sixteen  feet 
away.  The  lantern  is  shifted  back  and  forth  until  the  distance 
between  ^5218  and  ^5105  is,  we  will  say,  thirty  centimeters. 
The  wave  length  difference  between  these  two  lines,  as  can  be 
seen,  is  one  hundred  thirteen  Angstrom  units,  the  linear  differ- 
ence is  thirty  centimeters,  hence  thirty  cm.  equals  113  A.  U.,  one 
m.  m.  equals  113-300  A.  U.  Now  to  measure  any  line  between 
the  two  standards,  one  must  get  the  linear  distance  from  either 
of  the  standards  to  this  line,  and  convert  the  distance  into  A.  U. 
as  shown  above,  and  add  it  to  or  subtract  it  from  the  standard, 
according  to  whether  the  measurement  is  made  in  the  direction 
of  the  red  or  violet  end. 

The  dispersion  not  being  precisely  equal  for  all  colors,  new 
values  of  A.  U.  in  m.  m.  must  be  taken  between  new  standards, 
as  the  measurement  progresses  along  the  spectrum. 

Seed's  Panchromatic  plates  were  used  at  first,  and  then  Cra- 
mer's "Pan  Iso  Plates"  were  adopted,  the  latter  being  very  sensi- 
tive to  the  red  rays. 


0 

o 
o 


§ 


§ 


Figure  3 


14 

About  twelve  dozen  plates  Were  developed  with  from  eight 
from  twelve  spectra  on  each  plate,  making  a  total  of  about  eleven 
hundred  spectra  examined. 


THE  ARC  SPECTRUM  OF  TANTALUM. 

Following,  the  wave  lengths  of  the  tantalum  spectrum  will 
be  given  from  ^3  200  to  ^6300. 

The  intensities  range  from  i,  for  the  lines  easily  visible,  to  10, 
for  the  strongest  lines,  in  the  copper  spectrum,  o  is  used  for 
lines  just  visible.  An  n  denotes  nebulous,  a  line  not  sharply 
denned ;  s  denotes  sharp ;  b  denotes  band ;  and  is  inclosed  in 
brackets,  the  wave  lengths  of  the  two  edges  being  given.  A  D 
following  a  character  letter  (as  sD)  means  double.  After  some 
of  the  lines  will  be  seen  the  symbol  of  an  element  followed  by 
a  question  mark,  indicating  that  the  probability  is  that  the  line 
belongs  to  the  element  mentioned,  Which  might  have  occurred 
in  the  spectrum  as  an  accidental  impurity. 
Wave  Length.  Intensity.  Character.  Wave  Length.  Intensity.  Character. 


6268 
6264 

6252 

0248 
6203 

6195 
6049 

6041 

6034 
6010 
6000 

5996 

5990 
5987 
5978 
5974 
5970 
5963 
5938 
5934 
5931 
5923 


5907 
5887 
5883 
5873 


sD 

s 

s 

s 

s 

n 

s 

s 

s 

s 

s 

n 

n 

n 

n 

n 


5870 
5863 
5859 
5856 
5848 
5847 
5842 
5837 
5830 
5820 


5810 
5808 
5805 
5792 
5787 
5782 
5696 
5692 
5687 
5682 
5642 
5635 
5631 
5619 
5614 
5611 


3 

s 

I 

s 

I 

s 

I 

s 

I 

s 

I 

s 

2 

s 

2 

s 

I 

n 

I 

n 

0 

s 

0 

s 

o 

s 

4 

s 

i 

s 

i 

s 

i 

s 

6 

s 

4 

s 

2 

n 

4 

s 

3 

n 

2 

n 

iSn? 

n 

i 

s 

i 

s 

i 

s 

15 


Wave  Length. 

Intensity.  < 

Character. 

Wave  Length. 

Intensity.  C 

:hara 

5606 

i 

s 

.   5348 

s 

5605 

o 

n 

5340 

s 

5602 

0 

n 

5336 

s 

5595 

i 

n 

5334 

s 

5564 

o 

s 

5330 

s 

556o 

o 

s 

5328 

s 

5530 

I 

n 

5327 

s 

55i8 

2 

n 

5324 

s 

5497 

I 

n 

5322 

2 

s 

5494 

I 

n 

5317 

2 

s 

5492 

I 

n 

5313 

i 

n 

5488 

2 

s 

5307 

I 

s 

5482 

I 

s 

5304 

i 

s 

5478 

I 

s 

5302 

I 

s 

5473 

I 

s 

5298 

3Cb? 

n 

5467 

I 

s 

5294 

8 

s 

5463 

I 

n 

.5289 

3 

s 

5459 

2 

s 

5062 

8 

s 

5456 

I 

s 

5055 

2 

s 

5450 

I 

s 

5052 

2 

n 

5449 

I 

s 

5050 

I 

s 

5447 

I 

s 

5047 

I 

s 

5444 

I 

n 

5045 

2 

n 

5440 

I 

s 

5044 

I 

s 

5436 

1 

s 

5040 

2 

s 

5433 

I 

s 

5034 

3 

s 

5431 

I 

sD 

5031 

I 

s 

5420 

I 

s 

5022 

0 

n 

54i8 

I 

s 

5016 

0 

n 

54U 

I 

s 

5012 

o 

n 

51T° 

1 

s 

5009 

0 

n 

5407 

I 

s 

5003 

I 

nD 

5405 

I 

s 

5000 

oTi-La? 

n 

5400 

5 

s 

4996 

o 

n 

5397 

iFe? 

s 

4993 

i 

n 

5393 

s 

4989 

i 

n 

5391 

s 

4988 

i 

V 

5388 

s 

4986 

i 

n 

5382 

s 

4980 

2 

s 

5378 

s 

4976 

2 

s 

5372 

s 

4972 

I 

s 

5369 

s 

4870 

I 

n 

5366 

s 

4965 

I 

n 

536o 

s 

4951 

3 

s 

5356 

n 

4949 

i 

s 

5354 

s 

4940 

i 

s 

5352 

s 

4938 

I 

s 

16 


Wave  Length. 

Intensity.  Character.  Wave  Length. 

Intensity.  Character. 

4927  \ 
4865) 

J2Fe.Ti. 
(2Fe.Ti. 

Cb?  nb 
Cb?nb 

4118 
4113 

3 
3 

s 
s 

4850 

2 

n 

4109 

2 

s 

4847 

I 

n 

4105 

2 

s 

4837 

2 

.  s 

4095 

2 

s 

4834 

2 

s 

4091 

2 

s 

4829 

3 

n 

4074 

2 

s 

4826 

3 

n 

4070 

2 

s 

4823 

2Mn? 

s 

3996 

2 

n 

4821 

I 

s 

3989 

2 

n 

4819 

I 

s 

3986 

2 

n 

4815 

o 

s 

3983 

2 

s 

4812 

2 

s 

3979 

2  Cb? 

n 

4810 

3 

s 

3975 

2 

s 

4807 

i 

n 

3971 

2 

s 

4803 

2 

s 

3969 

2 

s 

4800 

n 

3961 

4 

s 

4769 

s 

3956 

2  FeCa 

s 

4764 

s 

3952 

2 

s 

4754 

s 

3947 

2 

s 

4752 

s 

3944 

2 

s 

4686 

2 

s 

3926 

2 

s 

4656 

2 

n 

3921 

I 

n 

4637 

2 

s 

3914 

4 

s 

4582 

s 

3910 

4 

s 

4577 

s 

3905 

s 

4458 

s 

3901 

s 

4432 

s 

3900 

s 

4430 

s 

3898 

s 

4427 

s 

3896 

s 

4424 

s 

3888 

s 

4421 

s 

3881 

s 

4397 

s 

3874 

3 

s 

4387 

s 

3851 

i 

s 

4376 

Fe? 

s 

3787 

3 

s 

4372 

0 

s 

3785 

3 

s 

4362 

0 

s 

378i 

2 

n 

4357 

o 

s 

3778 

4 

s 

4267 

s 

3774 

2 

s 

4240 

s 

3770 

2 

s 

4214 

s 

3768 

I 

s 

4211 

s 

3764 

2 

s 

4207 

s 

3691 

3 

s 

4205 

s 

3686 

3 

s 

4204 

s 

3682 

4 

s 

4198 

s 

3678 

7 

s 

4188 

s 

3672 

3 

s 

17 
Wave  Length.  Intensity.  Character.  Wave  Length.   Intensity.  Character 

3670  5  s  3462  i  s 

3669  3  s  3456  i  s 

3667  i  s  3452  i  s 

3665  3  s  3448  o  Cb?          s 

3659  2  s  3446  o  s 

3651  2  s  3440  5  n 

3649  3  s  3430  o  s 

3640  3  Fe  ?           s  3423  5  n 

3639  2  Fe?         s  3414  o  3 

3635  4  s  3412  o  s 

3631  2  Fe?         s  3405  o  s 

3620  4  s  3397  o  s 

3612  2  Fe?          n  3395  o  n 

3590  4  s  3393  o  n 

3586  2  s  3390  o  n 

3584  2  s  3387  o  n 

3576  2  s  3385  o  n 

3572  2  s  3383  o  n 

3567  3  s  3380  o  n 

3554  5  "D  3378  o  s 

3547  5  n  3375  o  s 

3545  i  s  3371  o  s 

3542  5  nD  3368  o  s 

3538  4  s  3366  o  s 

3532  2  s  3361  o  s 

3520  2  s  3347  o   Cb?          s 

3507  3  n  3345  o  s 

3503  2  s  3339  o  s 

3499  2  s  3333  °  s 

3496  2  s  3306  o   Fe?          s 

3493  i  s  ,3300    ^  o  s 

3491  5  Cb?          n  3297  o  s 

3489  i  s  3295  o  s 

3487  i  s  3292  o  s 

3485  5  n  3287  o  s 

3482  i  s  3283  o  s 

3480  i  s  3280  o  s 

3475  2  n  3262  o  s 

3471  2  s  3257  i  s 

3470  i  n  3251  i  s 

3466  i  n  3246  i  s 

In  the  spectrum  of  columbium  recently  published  by  Hilde- 

brand*  there  are  several  lines  to  be  found,  which  correspond 


*J.  Am.  Ch.  S.  30,  1677. 


18 

both  in  wave  length  and  in  intensity,  to  lines  found  in  the  spec- 
trum of  tantalum.  There  is  every  reason  to  suppose  that  the 
Cb2O5  used  by  Hildebrand  was  as  pure  as  could  be  prepared, 
With  the  present  knowledge  of  columbium  and  its  allied  elements. 
And  since  We  have  the  same  assurance  with  regard  to  the  Tb2C>5 
used  in  this  work,  there  is  either  an  unknown  element  associated 
with  tantalum  and  columbium  or  a  common  impurity  inseparable 
by  the  methods  used  in  purification ;  for  if  the  impurity  in  the 
specimen  of  Tb2C>5  used  by  us  was  columbium,  the  lines  should 
appear  weaker  in  the  tantalum  spectrum,  and  vice  versa. 

Following,  the  coincident  lines  are  given.  To  the  right  are 
the  tantalum  lines  with  intensity,  to  the  left  are  Hildebrand 's 
lines  for  columbium. 

Wave  Length.  Intensity.  Wave  Length.  Intensity. 

5366.0  I         5366  I 

5340.1  I         5340  I 
5321.9             2         5322              2 

5317.1  2  5317  2 
5302.4                  I             5302  I 

f  5054.9  2  5055  2 

4992.6  I  4993  I 

4764-0  I  4764  I 

4357-0  i  4357  o 

4203.6  I  4204  I 

3764.2  2  3764  2 

3667.1  I        3667  I 

3496.2  2  3496  2 

3387-1  i         3387  o 

3361.0  i         3361  o 

3262.0  i         3262  o 

The  following  lines,  which  appear  in  the  tantalum  spectrum, 
do  not  appear  in  Exner  and  Hascheck's  Spectrum  of  Columbium, 
but  are  attributed  to  this  latter  element  by  Hildebrand*  and 
inserted  in  his  table  of  wave  lengths.  To  the  right  are  the  tanta- 
lum lines,  to  the  left  are  Hildebrajid's  lines: 

Wave  Length.  Intensity.  Wave  Length.  Intensity. 
3888.6                                I                       3888  I 

3287.1  i  3287  o 

3257.2  i  3257  o 


*Loc.  cit. 


19 

The  following  strong  lines  are  unidentified  in  Rowland's  Solar 
Spectrum,*  and  are  probably  due  to  tantalum : 

Wave  Length.                Intensity.       Wave  Length.  Intensity. 

5682.427                             2                        5682  4 

5012.335                            i                       5012  o 

5031.199                             3                        5031  i 

3910.469                                                      3QIO  4 

3910.670  2j 

3682.310            2          3682  4 

3554-593           2         3554  5 
3538.643 
3538.399 

SPECTRUM  OF  A  CLAY  RESIDUE. 

Below  are  given  the  Wave  lengths,  which  occur  in  the  spec- 
trum of  precipitate  A,  and  which  have  not  been  positively  identi- 
fied. The  lines  corresponding  to  Ti,  Ta,  Fe,  Na,  etc.,  have  been 
removed  from  the  table : 

5890              2  Na?         s                     4940              4  s 

5885               2                  s                      4275               4  Cr?  s 

5883                2                    s                        4110                 3  .  n 

5880                2                    s                        4100                3  Cb?  n 

5875                3                    s                        4094                3  n 

5866                2                   n                        3995                3  s 

5860                3                   n                        3990                6  s 

5853               3  Ba?            s                       3982               6  s 

5850               3                   s                       3973               7  Ca?  s 

5844               8                   s                       3951                8  n 

5834               8  Cb?           s                       3942               9  n 

5749              10                   s                       3931                6  n 

5167               4  Mg?          s                       3919                5  Cb?  s 

4946               2  Cb?           s                       3909               5  Cb?  s 

The  following  lines  are  unidentified  in  Rowland's  Solar  Spec- 
trum, and  occur  in  the  spectrum  of  precipitate  A. 

Wave  Length.                Intensity.       Wave  Length.  Intensity. 

4094.573                            2n                     4094  3n 

3995.352                            2                       3960  6 

3990.248                            o                       3942  9 

3942.510                            2                       3931  6 

3942.380                            o                       2995  2 
3931.030                            o 


*See  Rowland's  Solar  Spectrum. 


2(1 


SUMMARY. 


1 .  The  arc  spectrum  of  tantalum  has  been  measured  between 
^3200  and  ^6300. 

2.  The  method  of  using  H2SO4  and  HNC>3   for  obtaining 
clays  in  solution,  is  satisfactory. 

3.  The  spectrographic  method  for  examining  precipitates,  for 
rare  elements  and  traces,  is  pre-eminently  superior  to  ordinary 
spectroscopy. . 

4.  There  is  probably  an  unknown  element  associated  with 
columbium  and  tantalum,  or  a  common  impurity,  inseparable 
from  either  element,  by  ordinary  means  of  purification. 

5.  There  is  a  doubtful  element  or  group  of  elements  in  the  clay 
from  Spruce  Pine,  Alabama. 

6.  Tantalum  has  been  identified  as  one  of  the  metals  in  the 
sun  from  lines  which  Were  marked  unknown  by  Rowland. 


4698o-i 


c 


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